Methods of preparing sand cores and other sand mould parts for metal casting



METHODS OF PREPARING SAND CORES OTHER SAND MOULD PARTS FOR CASTING.

Rolf Erhard Morn, Alfredshem, Swedemyassignor to M och Dornsjii Alrtiebolag, Ornskoldsvik, Sweden, a corporation of Sweden No Drawing. Application October 4, 1955 Serial No. 538,533

Claims priority, application Sweden October 6, 1954 4 Claims. (Cl. 106-385) The present invention relates to sand cores and other sand mould parts for metal casting and more particularly concerns a binder combination for said purpose.

When preparing cores in foundries, use ismost often made of oils of different kinds, so-called core oils, as binders. Often crude or boiled linseed oil is used, but

States Patent 0 derivative-cores which leadsr to lower costs of de-coring.

The cellulose derivative may advantageously beused also tall oil, fish oils, soya-bean oil and petroleum prodnets are used. The oils impart a good dry strength to the core, but on the other hand they impart little green strength, wherefore they are generally combined with preparations based on' swelled starch in order that the core shall be capable of being handled in the green state.

It has been found that important advantages may be gained if instead of starch the core oils are combined with water-soluble cellulose derivatives as additives to the sand in order to impart to the cores the desired green strength.

' l 2,838,406 Icfi Patented June 10, 195

surfaces on the castings. A considerably more rapid decomposition after the casting is also noted in the cellulose in a -pure form together with the oils. lfdesired, however, it may also be admixed with extenders, such as wood flour, clay etc. When using such, an. extended cellulose derivative, somewhat greater amounts of the preparation will, of course, have to be used in. order to-achieve. acomparable green strength, but since the price of the prepara tion will be lower, it will still be more advantageousthan the starch from a cost viewpoint.

Suitable cellulose derivatives include e. g. water-soluble cellulose ethers, such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, methyl or ethyl hydroxyethyl cellulose, water-solube salts;o,f cellulose ether carboxylic acids, such as sodium carboxymethyl cellulose, cyanoethyl cellulose, sulphoethyl cellulose, and further sodium salts of cellulose sulphuric acid esters. Such water-soluble cellulose derivatives, and methods of their preparation are well-known in the art, and they arecommercially available.

The amount of cellulose derivative added to the sand may be (Ll-2. parts by weight per 1.00 parts by weight. of

Thus it was found that these cellulose derivatives impart a considerably greater green. strength than does the starch when used in equal quantities, or in other words to obtain a desired green strength a smaller amount of the cellulose derivative than of starch need be used. Indeed, the properties of the cellulose derivatives are so advantageous in the danger of gas cavities in the castings. Furthermore,

the gas permeability of the cores is increased.

As regards the dry strength, this is in some cases somewhat lower in cores based on cellulose derivatives (when the comparison is made on the basis of amounts which are equivalent with respect to cost), but thevalues obtained with the cellulose derivatives are in any case wholly sufiicient for the storage of the cores and their transport to the place of casting. It is also to be noted that the cellulose derivatives generally (an exception is e. g. carboxymethyl cellulose) are less hygroscopic than starch and can be added in smaller amounts. Since casting is in most cases performed in raw sand moulds and since the core will as a rule be stored in the raw sand mould for some time before the casting operation takes place, the

starch will have an opportunity of absorbing a rather sand depending on the desired green strength while the amount of core oil will generally be within the: range of 0;5'-5 parts by weight per 100 parts by weight of sand. In addition water'will be added, if necessary, in an amount such that the final moisture content of the sand mix will be 2-7% by weight. Of course, it is within the scope of the invention to add, if desired, other binders and additives, which may be considered preferable in special cases. It is further who noted that while the invention primarily contemplates. cores, it 'will be possible to make other sand mould parts according; to the invention, if desired.

7 The invention can be utilized in connection with the casting of all kinds of metals and alloys, such as steel,

iron, copper,-aluminum, lead etc.

The invention is illustrated, but not limited by the following examples:

' Example 1 0.5 part by weight of pulverized water-soluble ethyl hylroxyethyl cellulose was admixed to 100 parts by weight of sea sand, whereupon waterwas added in an amount such that the final moisture content in the sand mix was 4.0% by Weight. After 6 minutes of blending the sand in an edge-runner mill a core oil (based on tall oil products) was added and blended with the sand mix for 2 minutes. When testing test cores in standard testing equipment the following strength values of the core sand mix were obtained:

7 Green com- Dry bending presslon strength, gs. Core 011, parts by weight strength. per sq. mm. gs. per (averages of sq. cm 4 tests With a standard core flour (swelled cereal binder), added in an amount of 2.0% by weight, i. e. in an amount corresponding on a cost basis to 0.5% by weight'of the above ethyl hydroxyethyl cellulose, the following values were obtained when an otherwise similar procedure was employed.

Green eom- Dry bending Green com- Dry bending presslon strength, gs. pression strength, gs. Oore oil, parts by weight strength, per sq. mm. Linseed 011, parts by weight strength. gs. per sq. mm. gs. per (P1 8 per sq. em. (average sq. cm 4 tests 5 4 tests) 1.5 347 1.0-"; as see 2 o 70 400 V a After storing the baked cores for 1 hour in raw mould .In each case, the dry bending strength was determined 10 on cores which were baked for 1% hours at 200 C.

Example 11 1.0 part by weight of a composition comprising 50% by weight of rye flour and 50% by weight of pulverised water-soluble ethyl hydroxyethyl cellulose was admixed to 100 parts by weight of sea sand, whereupon an amount of water was added to bring the total moisture content of the sand to 3.4% by weight. After blending the mix for 6 minutes in an edge-runner mill crude linseed oil was added tothe sand and admixed for 2 minutes. Test cores weremade and tested in standard testing equipment. The following results were obtained.

Green compression strength, gs.

Linseed 011, parts by weight per sq. em.

Green oom- Dry bending presston strength, gs. per sq. mm. (azerage of Linseed 011, parts by weight tests) I per sq. cm.

In each case, the dry bending strength was determined on cores baked for 1% hours at 200 C.

Example Ill 0.85 part by Weight of a composition comprising 40% by weight of pulverised water-soluble ethyl hydroxyethyl .cellulose and 60% by weight of rye flour was admixed to 100 parts by weight of sea sand, whereupon water was added to bring the final moisture content of the sand mix to 3.6% by weight. After blending the mix for 6 minutes in an edge-runner mill, crude linseed oil was added and admixed for 2 minutes. Test cores were tested in standard testing equipment and the following strength values of the core sand mix were obtained.

sand, the dry bending strength value decreased to 185 gs. per sq. mm.

In each case the dry bending strength was determined on cores baked for 1 hours at 200 C.

Example IV Green com- Dry bendlng presslon strength. gs. Core oil, parts by weight strength, per sq. mm. gs. pet (averages of sq. cm. 4 tests After storing baked cores for 1 hour in raw moulding sand, the dry compression strength value decreased to 260 gs. per sq. mm.

With a standard core fiour,'added in an amount of 1.5 parts by weight, i. e. to a cost about equal to that of the above binder composition, the procedure being otherwise the same, the following values were obtained.

Green com- Dry bending presslon strength, gs. Core 011, parts by weight strength, per sq. mm. gs. per (averages 0! sq. cm. 4 tests After-storing the baked cores for 1 hour in raw moulding sand, thedry bending strength value decreased to 180 gs. per sq. mm. t

In each case, the dry bending strength was determined on cores baked for 1% hours at 200 C.

Example V 1.2 parts by weight of a composition comprising 40% by weight of pulverized carboxymethyl cellulose and 60% by weight of rye flour was admixed to parts by weight of sea sand, whereupon so much water was added that the final moisture content of the sand mix 60 was 3.4% byweight. After blending the sand mix for 6 minutes in an edge-runner mill, crude linseed oil was 523253,? E ig' ggfif added and the mixture blended for 2 minutes. When Lin e 011, p y weight g s g 12322 5 2 3 tested in a standard testing equipment the following p testgs) 5 values for the core sand mix were obtained.

10 380 Green eom- Dry bending presslon strength, gs. Linseed oil, parts by weight strength, gs. per sq. mm. per sq. cm. (average of After stonng baked cores for 1 hour in raw mould ttests) sand, the dry compression strength value decreased to 70 I V 174 gs. per sq. mm.

60 333 With a standard core flour, added in an amount of 1.5%

by weight, i. e. at a cost about the same as that of the above binder composition, the procedure being otherwise identical, the following values were obtained.

After storing the baked cores for 1 hour in raw moulding sand, the dry bending strength value decreased to gs. per sq. mm.

With. a standard core flour-, added in an amount of 1.5 parts by weight, i. e. an amount cor-responding to' about the same cost as that of the abovebindercomposition, the

procedure being otherwise identical, the following values After storing the baked cores for 1 hour in raw moulding sand, the dry bending strength value decreased to 185 gs. per sq. mm.

In each case, the dry bending strength was determined on cores baked for 1 /2 hours at 200 C.

. ExampleVl 0.4 part by weight of a composition comprising 65% by weight of pul'verised water-soluble. ethyl hydroxyethyl cellulose, 15% by weight of rye flour and 20% by weight of melamine resin powder was admixed to 100 parts by weight of fine sea sand, whereupon water was added to bring the final moisture content of the sand mix to 4.2% by weight. After blending the mix for 6 minutes in an edge-runner mill 1.0 part by weight of linseed oil was added and admixed for 2 minutes. When tested in a standard testing equipment the following values of the core sand mix were obtained.

Green compression strength: 63 gs. per sq. cm. Dry bending strength after 1 /2 hours of baking at 200 C:

308 gs. per sq. mm.

When stored in moisture-saturated air, the cores absorbed the following amounts of water:

After 1 After 6 After 24 hour hours hours After storing the cores for 24 hours in air saturated with moisture the dry bending strength of the cores had Green compression strength: 65 gs. per sq. cm. Dry bendingstrength after 1 /2 hours of baking at 200 C: 363 gs. per sq. mm.

When stored in air saturated with moisture, the cores absorbed the following amounts of water:

After 1 After 6 After 24 hour hours hours After storage for 24 hours in air saturated with moisture, the dry bending strength of the cores had decreased from 3-63 to 77 gs. per sq. mm.

Example VII 0.3 part by weight of pulverisedv pure water-soluble ethyl hydroxyethyl cellulose was admixed to 100 parts by weight of fine sea sand, whereupon water was added to bring the final moisture content of the sand to 4.1% by weight. After blending the mix for 6 minutes in an and the mix blended for 2 minutes;

. 6 I edge-runner mill 1.0 partbyweight of 'l inse'ed o' 1 was added and the mix blended for 2 minutes more. Whentested in standard testing equipment the following values of the core sand mix were obtained. Green compression strength: 68. gs. per sq acm Dry bending strength after 1 /2 hours ofbaking 'at, 200,

C: 318 gs.-per sq. mm. 7 '1 When stored in air saturatedwith 'moisturethecores absorbed the following amounts of Water:

After 14 I hours After 1 After 6 1 'hours hour After 24 hours of storage in-air saturated with moisture, the. drybending; strength of thecores had decreased; from 318 to 125 gs. per sq. mm. 7

- With a standard core flour, addedv in an amount of 1.5 parts by weight, i e. anamount, corresponding on a, cost basis tovthe above amount of ethyl. hydroxyethyl cellulose, the procedure being otherwise identical, using the same grade of linseed oil, the following values were obtained.

Green compression strength: 65 gs. per sq. cm.

Dry bending strength after 1 /2 hours of baking at 200 C.: 363 gs. per sq. mm.

When stored in air saturated with moisture, the cores absorbed the following amounts of water:

After 6 hours After 24 hours After 1 hour Example VIII 1.0 part by Weight of a composition comprising 40% by weight of water-soluble ethyl hydroxyethyl cellulose and 60% by weight of pulverized tall oil rosin was admixed to 100 parts by weight of fine sea sand, whereupon water was added to bring the final moisture content of the sand mix to 3% by weight. After blending the sand mix for 6 minutes in an edge-runner mill, 1.0 part by weight of linseed oil was added and the mix blended for 2 minutes more. When testing in standard testing equipment, the following values for the core sand mix were obtained.

Green compression strength: gs. per sq. cm. Dry bending strength after 1 /2 hours of baking at 200 C.: 536 gs. per sq. mm.

Example IX 1.0 part by Weight of a composition comprising 40% by weight of water-soluble ethyl hydroxyethyl cellulose, 40% by weight of tall oil rosin and 20% by weight of molasses was admixed to parts by weight of fine sea sand, whereupon Water was added to bring the final moisture content of the sand mix to 3% by weight. After 6 minutes of blending the sand'mix in an edgerunner mill, 1.0 part by weight of linseed oil was added standardtesting equipment, the following strength values for the core sand mix were obtained.

Green compression strength: 97 gs. per sq. cm. Bending strength: 625 gs. per sq. mm.

Castings have been made on cores prepared in accord ance with the present invention and comprising as binders When tested in water-soluble ethyl hydroxyethyl cellulose in combination with linseed oil and rye-flour-extended ethyl hydroxyethyl cellulose in combination with tall oil, and on cores comprising as binders starch combined with linseed oil and with tall oil. The castings were carried out so that the'conditions were as far as possible similar, in that iron of the same analysis and of the same temperature when poured into the moulds was used as well as moulds'and cores of the same configuration and prepared and treated in the same manner. The amounts of starch and cellulose derivative were such that they were equivalent from the point of view of cost. It was found that the cellulose-ether-bound cores collapsed more satisfactorily than the starch-bound cores after the casting operation and that when the first-mentioned cores were used the castings had a smoother surface than when the starch-bound cores were used. Having now particularly described the nature of my invention and the manner of its operation what I claim is: i

1. A sand mix suitable for the production of sand cores and other sand mould parts for metal casting con- 'sisting essentially of sand, and including 0.1 to 2 parts References Cited in the file of this patent UNITED STATES PATENTS 2,143,930 Anderson; Jan. 17, 1939 2,252,527 Sherk et al. Aug. 12, 1941 2,338,802 Decker Ian. 11, 1944 2,398,047 Schmidt Apr. 9, 1946 2,583,036 Wolf Q. Jan. 22, 1952 FOREIGN PATENTS 1,079,046 France May 19, 1954 231,934 Switzerland July 17, 1944 

1. A SAND MIX SUITABLE FOR THE PRODUCTION OF SAND CORES AND OTHER SAND MOULD PARTS FOR METAL CASTING CONSISTING ESSENTIALLY OF SAND, AND INCLUDING 0.1 TO 2 PARTS BY WEIGHT OF A WATER-SOLUBLE CELLULOSE DERIVATIVE PER 100 PARTS OF SAND 0.5 TO 5 PARTS BY WEIGHT OF A CORE OIL PER 100 PARTS OF SAND AND 2 TO 7 PARTS BY WEIGHT OF MOISTURE PER 100 PARTS OF SAND 